/*
 * Based on arch/arm/include/asm/uaccess.h
 *
 * Copyright (C) 2012 ARM Ltd.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#ifndef ASM_UACCESS_H
#define ASM_UACCESS_H

#include <asm/barrier.h>

#define get_ds()	(KERNEL_DS)
#define get_fs()	(current_thread_info()->addr_limit)

static inline void set_fs(mm_segment_t fs)
{
    current_thread_info()->addr_limit = fs;

    /*
     * Prevent a mispredicted conditional call to set_fs from forwarding
     * the wrong address limit to access_ok under speculation.
     */
    spec_bar();

    /* On user-mode return, check fs is correct */
    set_thread_flag(TIF_FSCHECK);

    asm("nop");
}

#define segment_eq(a, b)	((a) == (b))

/*
 * Test whether a block of memory is a valid user space address.
 * Returns 1 if the range is valid, 0 otherwise.
 *
 * This is equivalent to the following test:
 * (u65)addr + (u65)size <= (u65)current->addr_limit + 1
 */
static inline unsigned long __range_ok(const void __user *addr, unsigned long size)
{
    unsigned long ret, limit = current_thread_info()->addr_limit;

    __chk_user_ptr(addr);
    asm volatile(
    // A + B <= C + 1 for all A,B,C, in four easy steps:
    // 1: X = A + B; X' = X % 2^64
    "	adds	%0, %3, %2\n"
    // 2: Set C = 0 if X > 2^64, to guarantee X' > C in step 4
    "	csel	%1, xzr, %1, hi\n"
    // 3: Set X' = ~0 if X >= 2^64. For X == 2^64, this decrements X'
    //    to compensate for the carry flag being set in step 4. For
    //    X > 2^64, X' merely has to remain nonzero, which it does.
    "	csinv	%0, %0, xzr, cc\n"
    // 4: For X < 2^64, this gives us X' - C - 1 <= 0, where the -1
    //    comes from the carry in being clear. Otherwise, we are
    //    testing X' - C == 0, subject to the previous adjustments.
    "	sbcs	xzr, %0, %1\n"
    "	cset	%0, ls\n"
    : "=&r" (ret), "+r" (limit) : "Ir" (size), "0" (addr) : "cc");

    return ret;
}

#define access_ok(addr, size)	__range_ok(addr, size)
#define user_addr_max			get_fs

#define _ASM_EXTABLE(from, to)						\
    "	.pushsection	__ex_table, \"a\"\n"			\
    "	.align		3\n"					\
    "	.long		(" #from " - .), (" #to " - .)\n"	\
    "	.popsection\n"

/*
 * Sanitise a uaccess pointer such that it becomes NULL if above the
 * current addr_limit.
 */
#define uaccess_mask_ptr(ptr) (__typeof__(ptr))__uaccess_mask_ptr(ptr)
static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
{
    void __user *safe_ptr;

    asm volatile(
    "	bics	xzr, %1, %2\n"
    "	csel	%0, %1, xzr, eq\n"
    : "=&r" (safe_ptr)
    : "r" (ptr), "r" (current_thread_info()->addr_limit)
    : "cc");

    csdb();
    return safe_ptr;
}

/*
 * The "__xxx" versions of the user access functions do not verify the address
 * space - it must have been done previously with a separate "access_ok()"
 * call.
 *
 * The "__xxx_error" versions set the third argument to -EFAULT if an error
 * occurs, and leave it unchanged on success.
 */
#define __get_user_asm(instr, alt_instr, reg, x, addr, err)	\
    asm volatile(							\
    "1:"instr "     " reg "1, [%2]\n"		\
    "2:\n"								\
    "	.section .fixup, \"ax\"\n"				\
    "	.align	2\n"						\
    "3:	mov	%w0, %3\n"					\
    "	mov	%1, #0\n"					\
    "	b	2b\n"						\
    "	.previous\n"						\
    _ASM_EXTABLE(1b, 3b)						\
    : "+r" (err), "=&r" (x)						\
    : "r" (addr), "i" (-EFAULT))

#define __get_user_err(x, ptr, err)					\
do {									\
    unsigned long __gu_val;						\
    switch (sizeof(*(ptr))) {					\
    case 1:								\
        __get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr),  \
                   (err));			\
        break;							\
    case 2:								\
        __get_user_asm("ldrh", "ldtrh", "%w", __gu_val, (ptr),  \
                   (err));			\
        break;							\
    case 4:								\
        __get_user_asm("ldr", "ldtr", "%w", __gu_val, (ptr),	\
                   (err));			\
        break;							\
    case 8:								\
        __get_user_asm("ldr", "ldtr", "%x",  __gu_val, (ptr),	\
                   (err));			\
        break;							\
    default:							\
        BUILD_BUG();						\
    }								\
    (x) = (__typeof__(*(ptr)))__gu_val;			\
} while (0)

#define __get_user_check(x, ptr, err)					\
({									\
    __typeof__(*(ptr)) __user *__p = (ptr);				\
    if (access_ok(__p, sizeof(*__p))) {				\
        __p = uaccess_mask_ptr(__p);				\
        __get_user_err((x), __p, (err));			\
    } else {							\
        (x) = 0; (err) = -EFAULT;				\
    }								\
})

#define __get_user_error(x, ptr, err)					\
({									\
    __get_user_check((x), (ptr), (err));				\
    (void)0;							\
})

#define __get_user(x, ptr)						\
({									\
    int __gu_err = 0;						\
    __get_user_check((x), (ptr), __gu_err);				\
    __gu_err;							\
})

#define get_user	__get_user

#define __put_user_asm(instr, alt_instr, reg, x, addr, err)	\
    asm volatile(							\
    "1:"instr "     " reg "1, [%2]\n"		\
    "2:\n"								\
    "	.section .fixup,\"ax\"\n"				\
    "	.align	2\n"						\
    "3:	mov	%w0, %3\n"					\
    "	b	2b\n"						\
    "	.previous\n"						\
    _ASM_EXTABLE(1b, 3b)						\
    : "+r" (err)							\
    : "r" (x), "r" (addr), "i" (-EFAULT))

#define __put_user_err(x, ptr, err)					\
do {									\
    __typeof__(*(ptr)) __pu_val = (x);				\
    switch (sizeof(*(ptr))) {					\
    case 1:								\
        __put_user_asm("strb", "sttrb", "%w", __pu_val, (ptr),	\
                   (err));			\
        break;							\
    case 2:								\
        __put_user_asm("strh", "sttrh", "%w", __pu_val, (ptr),	\
                   (err));			\
        break;							\
    case 4:								\
        __put_user_asm("str", "sttr", "%w", __pu_val, (ptr),	\
                   (err));			\
        break;							\
    case 8:								\
        __put_user_asm("str", "sttr", "%x", __pu_val, (ptr),	\
                   (err));			\
        break;							\
    default:							\
        BUILD_BUG();						\
    }								\
} while (0)

#define __put_user_check(x, ptr, err)					\
({									\
    __typeof__(*(ptr)) __user *__p = (ptr);				\
    if (access_ok(__p, sizeof(*__p))) {				\
        __p = uaccess_mask_ptr(__p);				\
        __put_user_err((x), __p, (err));			\
    } else	{							\
        (err) = -EFAULT;					\
    }								\
})

#define __put_user_error(x, ptr, err)					\
({									\
    __put_user_check((x), (ptr), (err));				\
    (void)0;							\
})

#define __put_user(x, ptr)						\
({									\
    int __pu_err = 0;						\
    __put_user_check((x), (ptr), __pu_err);				\
    __pu_err;							\
})

#define put_user	__put_user

extern unsigned long __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
#define raw_copy_from_user(to, from, n)					\
({									\
    __arch_copy_from_user((to), __uaccess_mask_ptr(from), (n));	\
})

extern unsigned long __arch_copy_to_user(void __user *to, const void *from, unsigned long n);
#define raw_copy_to_user(to, from, n)					\
({									\
    __arch_copy_to_user(__uaccess_mask_ptr(to), (from), (n));	\
})

#define INLINE_COPY_TO_USER
#define INLINE_COPY_FROM_USER

extern unsigned long __arch_clear_user(void __user *to, unsigned long n);
static inline unsigned long __clear_user(void __user *to, unsigned long n)
{
    if (access_ok(to, n))
        n = __arch_clear_user(__uaccess_mask_ptr(to), n);
    return n;
}
#define clear_user	__clear_user

extern long strncpy_from_user(char *dest, const char __user *src, long count);

extern long strnlen_user(const char __user *str, long n);

#ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
struct page;
void memcpy_page_flushcache(char *to, struct page *page, size_t offset, size_t len);
extern unsigned long __copy_user_flushcache(void *to, const void __user *from, unsigned long n);

static inline int __copy_from_user_flushcache(void *dst, const void __user *src, unsigned size)
{
    return __copy_user_flushcache(dst, __uaccess_mask_ptr(src), size);
}
#endif

#endif /* !ASM_UACCESS_H */
